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Grey literature

Epidemiology: Grey Literature

Grey literature has been defined as: 'That which is produced on all levels of government, academics, business and industry in print and electronic formats, but which is not controlled by commercial publishers.'1

Grey literature has also been broadly defined to include everything except peer-reviewed books and journals accepted by Medline. It has not been published in a conventional way, and can be difficult to identify and obtain through the usual routes, and for this reason it is known as ‘grey literature.’

Locating grey literature
Grey literature comprises a wide range of material including, government publications, reports, statistical publications, newsletters, fact sheets, working papers, technical reports, conference proceedings, policy documents and protocols and bibliographies.

Papers are often written to inform funding bodies about the results of research projects or to present preliminary results at conferences or as dissertations. Such material is disseminated quickly, often in limited numbers, and seldom undergoes any formal publication process. Even if it has not been peer reviewed its content may still be useful2 and the authors of systematic literature searches should make efforts to identify this type of literature.

However, identifying and tracing grey literature poses several challenges. Basic information such as author, publication date or publishing body may not be easily discerned, making it difficult to locate and then cite documents. Low print runs may also make it difficult to locate. This is less of an issue with internet publishing, but government or organisational reports, for example, are seldom linked from websites indefinitely.

The lack of editorial control may also raise questions about the authenticity and reliability of documents.3

Producers of grey literature
A wide range of organizations produce a significant amount of grey literature related to public health, health policy and epidemiology. These include;

  • Government health agencies, such as the Centers for Disease Control and Prevention and the National Institutes for Health in the United States, The UK Department of Health.
  • Non-profit organisations
  • Universities
  • Research centres
  • International agencies such as the World Health Organization (WHO) and UNAIDS.
  • Health Institutes
  • Professional organisations
  • Special interest groups

Grey literature on the internet
There is debate about the place of internet search engines in literature searching, and some scientists argue strongly that it is not a valid source of information. However, in reality, the internet has increasingly opportunities to access grey literature. Search engines such as Google have become a major source of grey literature that is accessible to a wide international audience.

Several websites that provide a gateway to this type of literature include:2

  • MAGiC (Managing Access to Grey Literature Collections)
  • GrayLIT Network
  • Gray literature: Resources for locating unpublished research
  • Google Scholar


  1. Fourth International Conference on Grey Literature: New Frontiers in Grey Literature. GreyNet, Grey Literature Network Service, Washington DC, USA, 4-5 October 1999.
  2. - Accessed 23/01/09
  3. Mathews B. Gray literature: Resources for locating unpublished research C&RL News 2004; 65: 3


© Helen Barratt, Maria Kirwan 2009